(1) Field of the Industrial Utilization
The present invention relates to an acid anhydride complex and a process for producing same, and to the composition etc. containing same.
The complex of the present invention can be utilized for the stabilization of acid anhydride compounds during storage, for the improvement of solubility of the acid anhydride compounds to organic solvents, for the viscosity control of polyamic acids, for the technology which is applicable to the manufacturing processes of an electronic device with the composition, varnishes, films, fibers, each of which is containing the acid anhydride complex, and the acid anhydride complex itself.
(2) Description of the Prior Art
An acid anhydride has superior characteristics as a cross-linking agent, a monomer for synthesis of polymers. But, an acid anhydride has strong reactivity in general, and cautious consideration is required for its storage and the condition of its usage. Especially, it is a big problem in the industry that an acid anhydride reacts with moisture in the air and loses its reactivity. For example, an acid anhydride has superior characteristics as a hardner of an epoxy resin, but its utilization is restricted by easiness of causing hydrolysis.
In case of synthesis of polyamic acids etc., hydrolysis of the acid anhydride causes lowering of reactivity as a monomer, and causes a problem to prevent the polymer from getting higher degree of polymerization. Hitherto, according to such unstability, the usage of an acid anhydride have been restricted in spite of its superior characteristics. Therefore, at the time of using an acid anhydride, a special treatment such as storage in dry condition, reactivation by heating just before the using, dehydration of a solvent, are required to prepare for the unstability of the acid anhydride.
In case of synthesis of a polyamic acid etc., the degree of polymerization changes greatly depending on the equivalent ratio of the acid anhydride monomer and a reactant monomer such as an amine. That is, the molecular weight increases to infinity theoretically at the exact equivalent ratio and decreases sharply with deviating the ratio from the equivalence. Accordingly, the molecular weight of the polymer can be controlled easily by controlling the equivalent ratio. A solution of an oligomer having small molecular weight is easy in handling because of its low viscosity even with a high concentration. But, a film having small molecular weight has a problem in mechanical strength.
On the other hand, a solution of a polymer having large molecular weight produces generally a strong film, but the solution has a problem that slight increment of the concentration of the solution causes sharp increment of viscosity and make it impossible to work with the solution.
The solubility of the acid anhydride mentioned above is very poor, for instance, an acid anhydride is soluble very slightly even in N-methylpyrrolidon which is recognized as having the most preferable solubility, and the small solubility is deemed as a big problem in use of acid anhydrides, but there have not been any suitable means to solve the problem.
At the present, a polymer solution having large molecular weight and having easiness in handling even with high concentration and also of superiority in heat resistance, mechanical strength, and resistance to chemicals after it is hardened, is needed widely. A method to use an oligoamic acid obtained by making the molecular weight of polyamic acid small, and a method to use an imide oligomer and an isoimide oligomer both of which have good solubility responds to the need mentioned above. The methods mentioned above made it possible to use a high concentration-low viscosity solution. The usage of the solution is aimed to make it easy to coat in spin coating etc. by using an oligomer solution, and to obtain a superior coating film by causing a reaction at the reactive end groups of the oligomer by heat treatment to get finally a large molecular weight polymer. As for the reactive end groups, a partially esterified acid anhydride, an ethynyl group, a vinyl group, and a biphenylene group etc. have been investigated. For instance, an electronic device manufactured with an oligomer having vinyl group or acetylene group as an end group of the molecule was disclosed in the Japanese Patent Application Laid-Open No. 60-120723 (1985).
A complex crystal having a molar ratio of 1:1 of pyromellitic acid (PMDA) and N,N-dimethylacetamide(DMAC) is described in the Journal of Polymer Science (Part II, vol. 1, pp. 3135-3150). But there are not any description on the properties of the complex and whether it may be convertible to polyimide.